By Jerry HirschFederal safety regulators opened a probe into a series of fires in Tesla Motors Inc. electric cars following crashes.

The National Highway Traffic Safety Administration said Tuesday that it would investigate why two of the expensive Tesla Model S sporty hatchbacks have caught fire this year following accidents in which the battery casing that serves as the undercarriage of the car cracked open.

A third fire, which took place in Mexico, won’t be part of the investigation because it is outside the agency’s jurisdiction.

NHTSA noted that in the two U.S. fires, one in Seattle and the other in Nashville, the battery monitoring system in the cars warned the drivers, allowing them to pull over and safely exit the vehicles before the battery emitted smoke and fire.